Oracle table Building, primary key, foreign key basic syntax ____oracle

Oracle Table-Building, primary key, foreign key basic syntax

-Create TABLE syntax:
CREATE TABLE Table name (
Field name 1 field type (length) is empty,
Field Name 2 field type is NULL
);

-Add primary key
ALTER TABLE name add constraint primary Key name primary key (field name 1);

-Add foreign keys:
ALTER TABLE name
Add constraint foreign Key name foreign key (field name 1)
References Association table (field name 2);

specify primary key and foreign key when creating a table

CREATE TABLE T_stu (
stu_id char (5) NOT NULL,
Stu_name VARCHAR2 (8) NOT NULL,
Constraint Pk_t_stu primary KEY (STU_ID)
);

the primary key and the foreign key are established together:
CREATE TABLE T_score (
Exam_score number (5,2),
Exam_date DATE,
Autoid number is not NULL,
stu_id char (5),
sub_id char (3),
Constraint Pk_t_score primary KEY (Autoid),
Constraint Fk_t_score_refe foreign key (stu_id)
References T_stu (stu_id)
)